1. Technical Field
The present invention relates to a robot hand that grasps an object by using a plurality of fingers and a robot.
2. Related Art
Robots are widely used in manufacturing involving welding and painting. Further, robot hands having a plurality of fingers capable of grasping an object have been developed, which allow robots to also be used for carrying, assembling, and otherwise handling a variety of parts.
A robot hand needs to grasp an object with a force of an appropriate magnitude that does not damage the object to be grasped. Further, a robot hand is desired to be able to move fingers as quick as possible when grasping an object from a viewpoint of increased productivity.
To simultaneously meet the requirements described above, the following technology has been proposed (see JP-A-2009-066685). First, fingers of a robot hand are driven under position control to approach a target position in the immediate vicinity of an object. The fingers of the robot hand are then allowed to come into contact with the object under position control while limiting their grasp force to an acceptable predetermined value (position control with force constraint). Thereafter, the object is grasped with a force of an appropriate magnitude under force control. The proposed technology allows the fingers of the robot hand to approach an object quickly under the position control and then grasp the object with a force of an appropriate magnitude under the force control. The series of events described above, driving the fingers of the robot hand to approach the object, allowing the fingers to come into contact with the object, and then allowing the fingers to grasp the object with a force of an appropriate magnitude, can smoothly proceed under the position control with force constraint.
The technology described in JP-A-2009-066685, however, requires each finger that comes into contact with an object to be provided with a contact sensor. Further, before the fingers of the robot hand come into contact with the object, the control needs to be switched from the position control to the position control with force constraint and then to the force control. This is problematic because the structure and control of the robot hand (or robot) are inevitably complicated.